One of the most common uses of light strings is for decoration and display purposes, particularly during Christmas and other holidays, and more particularly for the decoration of Christmas trees, and the like. Probably the most popular light sets currently available on the market, and in widespread use, comprise thirty-five or fifty miniature light lamps each, with each lamp typically having an operating voltage rating of 3.5 or 2.5 volts respectively, and whose filaments are connected in an electrical series circuit arrangement.
A string of lights may be made to flash, or turn on and off, by including a flasher light lamp as one of the light lamps of the string. Such a flasher light lamp typically includes a bi-metallic strip which conducts current to the filament. As the bimetallic strip heats up, it moves away from the filament and breaks the current connection, causing the bulb to turn off. The bi-metallic strip then cools and returns to the initial position, allowing current to flow and begin the on and off cycle again. All of the bulbs in such a light string turn on and off simultaneously, as the lights are connected in series.